1989 Gt Hatchback Build.....

welcome. You need to provide more information

What sie injectors
was this just a top end or a new motor
Who assembled the motor
what head gasket and bolts
Define runs horrible- does it run, surge, die, stall, sputter,
what is your FP set at
What is your timing set at
did you check pushrod length
did you run the codes
Did you check for vacuum leaks

You should need 24# inj with the correct MAF. I'd also add more timing. But if it's not running correctly/won't idle/stumbles etc I have suspicion you have a vac leak(intake gaskets are common) or a fuel/ignition problem.(also If there are no other codes)

Your injectors are too small. What size injectors is you MAF calibrated for?

theskitzofrantic said:

Should it run fine with all these mods even if it hasn't been tuned?

Click to expand...

Not likely...
You are sucking in a lot more air. That means you need more fuel in order the keep the air/fuel mixture correct. That means 24lb. injectors and a calibrated MAF, or a custom dyno tune and 24lb. injectors.

When you put in bigger injectors, you need a bigger fuel pump.



Fuel injector sizing & injector photos

Revised 26-Dec-2014 to add statement about figures are for flywheel HP and not rear wheel HP

Injector HP ratings: this flywheel HP, not rear wheel HP.
Divide flow rating by.5 and multiply the result by the number of injectors. This uses a 100% duty cycle. These ratings are for naturally aspirated engines at the flywheel.

Example:
19/.5 = 38, 38 x 8 = 304 HP
24/.5 = 48, 48 x 8 = 384 HP
30/.5 = 60, 60 x 8 = 480 HP
36/.5 = 72, 72 x 8 = 576 HP
42/.5 = 84, 84 x 8 = 672 HP

The preferred duty cycle is about 85% maximum, so for a safety factor multiply the final figure times .85.

19/.5 = 38, 38 x 8 = 304 HP x .85 = 258 HP
24/.5 = 48, 48 x 8 = 384 HP x .85 = 326 HP
30/.5 = 60, 60 x 8 = 480 HP x .85 = 408 HP
36/.5 = 72, 72 x 8 = 576 HP x .85 = 490 HP
42/.5 = 84, 84 x 8 = 672 HP x .85 = 571 HP

Remember that the above ratings are at 39 PSI. Increasing the pressure will effectively increase the flow rating. Example: a 19 lb injector will flow 24 lbs at 63 PSI, and a 24 lb injector will flow 30 lbs at 63 PSI.

See Stan Weiss' - Automotive Performance Software / Interactive JavaScript to Calculate Change in Fuel Injector Flow from change in Fuel Pressure to get the calculators used in these examples.

Here's the duty cycle explanation. Duty cycle is how much of the time the intake is open the injectors are turned on. The 85% figure means that for 85% of the time the intake valve is open, the injectors are spraying. The idea is that you want some percentage of the duty cycle left over so that you have some room to grow the process.

If you are at 100% and you need more fuel, all you can do is turn up the fuel pressure. That means the whole fuel curve from idle to WOT is affected. Maybe you are already too rich at idle, and turning up the fuel pressure makes it worse. If you had some injector duty cycle left to play with, a custom tune could use that where it is needed. That would not over richen the whole range from idle to WOT.

If you did turn up the fuel pressure, you might be able to change the injector duty cycle to get the air/fuel mixture ratio you want since the injectors will have extra fuel delivery capability.

With larger than stock injectors or higher that stock fuel pressure, you will need an aftermarket MAF that matches the injector size. The MAF “lies” to the computer to get a fuel delivery schedule that meets the engine’s needs and isn’t too rich or too lean. The best strategy is an aftermarket MAF and a custom tune to insure the best air/fuel ratio over all the RPM range.

Don't forget to increase the fuel pump size when you increase injector size or significantly increase the fuel pressure



Diagram courtesy of Tmoss & Stang&2birds


See the following website for some help from Tmoss (diagram designer) & Stang&2Birds (website host) for help on 88-95 wiring Mustang FAQ - Wiring & Engine Info Everyone should bookmark this site.

Ignition switch wiring
http://www.veryuseful.com/mustang/tech/engine/images/IgnitionSwitchWiring.gif

Fuel, alternator, A/C and ignition wiring
http://www.veryuseful.com/mustang/tech/engine/images/fuel-alt-links-ign-ac.gif

Complete computer, actuator & sensor wiring diagram for 88-91 Mass Air Mustangs
http://www.veryuseful.com/mustang/tech/engine/images/88-91_5.0_EEC_Wiring_Diagram.gif

Vacuum diagram 89-93 Mustangs
http://www.veryuseful.com/mustang/tech/engine/images/mustangFoxFordVacuumDiagram.jpg

HVAC vacuum diagram
http://www.veryuseful.com/mustang/tech/engine/images/Mustang_AC_heat_vacuum_controls.gif

TFI module differences & pinout
http://www.veryuseful.com/mustang/tech/engine/images/TFI_5.0_comparison.gif

Fuse box layout
http://www.veryuseful.com/mustang/tech/engine/images/MustangFuseBox.gif



Copied from the FORD RACING PERFORMANCE PARTS catalog:

PROPERLY SIZING FUEL SYSTEM COMPONENTS

Fuel Pumps
The following information is presented assuming the above information has been taken into consideration regarding BSFC, fuel pressure and specific gravity of the fuel being used. Most fuel pumps for electronic fuel injection are rated for flow at 12 volts @ 40 PSI. Most vehicle charging systems operate anywhere from 13.2v to 14.4v. The more voltage you feed a pump, the faster it spins which, obviously, will put out more fuel. Rating a fuel pump at 12 volts then, should offer a fairly conservative fuel flow rating allowing you to safely determine the pump’s ability to supply an adequate amount of fuel for a particular application.

As previously mentioned, engines actually require a certain WEIGHT of fuel, NOT a certain VOLUME of fuel per horsepower. This can offer a bit of confusion since most fuel pumps are rated by volume, and not by weight. To determine the proper fuel pump required, a few mathematical conversions will need to be performed using the following information. There are 3.785 liters in 1 US Gallon. 1 gallon of gasoline (.72 specific gravity @ 65° F) weighs 6.009 LBS.

To be certain that the fuel pump is not run to its very limit, which could potentially be dangerous to the engine, multiply the final output of the fuel pump by 0.9 to determine the capacity of the fuel pump at 90% output. This should offer plenty of ‘cushion’ as to the overall “horsepower capacity” of the fuel pump.

To determine the overall capacity of a fuel pump rated in liters, use the additional following conversions:
(Liters per Hour) / 3.785 = Gallons
Multiply by 6.009 = LBS/HR
Multiply by 0.9 = Capacity at 90%
Divide by BSFC = Horsepower Capacity
So for a 110 LPH fuel pump:
110 / 3.785 = 29.06 Gallons
29.06 x 6.009 = 174.62 LBS/HR
174.62 x 0.9 = 157 LBS/HR @ 90% Capacity
157 / 0.5 = 314 HP safe naturally aspirated “Horsepower Capacity”

Safe “Horsepower Capacity” @ 40 PSI with 12 Volts
60 Liter Pump = 95 LB/HR X .9 = 86 LB/HR, Safe for 170 naturally aspirated Horsepower
88 Liter Pump = 140 LB/HR X .9 = 126 LB/HR, Safe for 250 naturally aspirated Horsepower
110 Liter Pump = 175 LB/HR X .9 = 157 LB/HR, Safe for 315 naturally aspirated Horsepower
155 Liter Pump = 246 LB/HR X .9 = 221 LB/HR, Safe for 440 naturally aspirated Horsepower
190 Liter Pump = 302 LB/HR X .9 = 271 LB/HR, Safe for 540 naturally aspirated Horsepower
255 Liter Pump = 405 LB/HR X .9 = 364 LB/HR, Safe for 700 naturally aspirated Horsepower

Note: For forced induction engines, the above power levels will be reduced because as the pressure required by the pump increases, the flow decreases. In order to do proper fuel pump sizing, a fuel pump map is required, which shows flow rate versus delivery pressure.

That is, a 255 liter per hour pump at 40 PSI may only supply 200 liters per hour at 58 PSI (40 PSI plus 18 lbs of boost). Additionally, if you use a fuel line that is not large enough, this can result in decreased fuel volume due to the pressure drop across the fuel feed line: 255 LPH at the pump may only result in 225 LPH at the fuel rail.


My Comments:

A lot of people oversize the fuel pump by buying a 255LPH pump thinking that the fuel pump regulator will just pass the excess gas back to the tank. It does, but… Did you ever consider that circulating the fuel around as a 255 LPH pump does will cause the gas to pickup engine heat? What happens to hot gasoline? It boils off or pressurizes the fuel tank! With most of the 5.0 Mustangs having the carbon canister removed or disabled, the car stinks like gas, and the gas mileage drops since the hot fuel evaporates away into the air.

@theskitzofrantic I believe @joetrainer31 is selling some 24# injectors for $50. That's a decent deal and it's what you need. You also need to do as others have already suggested, check for vacuum leaks around your intake and other vacuum line connections.

theskitzofrantic said:

It currently has 19lb injectors
total rebuild bored to a 306
I put it together
fel-pro gaskets....ARP head bolts
stock fuel pressure regulator
10* btd on timing
only code is 31....it doesnt have an EGR valve though.....the idle is the main problem

Click to expand...

Unless some of the injectors are bad, then going to 24lb injectors wont fix your issue. So don't be surprised if you change injectors and the problem is still there. Assuming they are in good condition, the 19lb injectors are fine for you to try and work out any bugs.

theskitzofrantic said:

I don't know where I could have a vac. leak, I plugged all the unused ports on my intake and only other vac lines are for brake booster and fuel regulator

Click to expand...

Yes, I have 24lbs Ford inj for $50. If you suspect a vac leak idle the motor and start spraying brake cleaner. If there is a leak you will find it fast that way.

If you come to a very abrupt stop and the car dies. then you have a vacuum leak.

I also have this problem I bought a 1988 mustang 5.0 a month ago with a new engine at 34,000 miles. It was running fine till a couple of days ago now I have to give it gas for about 10 sec for it to stay on. Previous owner said it had cobra injectors.I'm buying a innova ford code reader soon to see what that says and I guess I'll check for vacum leaks mods are, trickle flow upper lower intake, e303 cam,gt40 heads, under drive pulleys, Air mass sensor from '87 70mm throttle body

Foxstang31 said:

I also have this problem I bought a 1988 mustang 5.0 a month ago with a new engine at 34,000 miles. It was running fine till a couple of days ago now I have to give it gas for about 10 sec for it to stay on. Previous owner said it had cobra injectors.I'm buying a innova ford code reader soon to see what that says and I guess I'll check for vacum leaks mods are, trickle flow upper lower intake, e303 cam,gt40 heads, under drive pulleys, Air mass sensor from '87 70mm throttle body

Click to expand...

Agreed with @A5literMan
You either bought a car that was MAF converted and then messed it up by putting an 87' speed density meter on your car or your car is speed density and needs to either be tuned for your modifications or converted to MAF (which came on 89-93 Mustangs with V8 engine) and get a matching MAF programmed for 24# injectors. You should however VERIFY that you have those injectors and don't just take the P.O.'s word as scripture.

FoxMustangLvr said:

Agreed with @A5literMan
You either bought a car that was MAF converted and then messed it up by putting an 87' speed density meter on your car or your car is speed density and needs to either be tuned for your modifications or converted to MAF (which came on 89-93 Mustangs with V8 engine) and get a matching MAF programmed for 24# injectors. You should however VERIFY that you have those injectors and don't just take the P.O.'s word as scripture.

Click to expand...

The previous owner was the one that did all the mods, how do I see if it has a 87' speed density meter? It has a maf it actually says Pro Flow 87mm so it's not from an 87' I guess I miss understood him. Also how do I see what injector size and brand I have? Sorry new to all this mustang stuff

@Foxstang31

First off we are thread jacking somebody right now. The best way to get the best help from everybody here is to start your own thread in the GENERAL TALK area and the info will quickly come rolling in to help you identify your combo. Pro Flow 87mm MAF? Doesn't sound right, it's way too big if that's even true.

Just made my own thread check it out